I clay at least twice a year. Just wash and dry the Jeep really good before hand. Be sure to use lots of lube too. I use the Meguiar's kit they sell at Walmart (the one with the clay bar and detail spray). If you have never done it before, take your time to get the hang of what is going on, go slow, and knead the clay often. Have lots of microfiber towels ready to go as you always want a clean side of the towel to wipe down the panel after you clay it. You will be able to tell when the panel you are working with is clean (it will glide like butter). You will be amazed at the amount of crap you will pull out of the paint and just how good you make your paint again. If you want to take things a step further, look into the Meguiar's DA correction kit.
Just checked Meguiar's site. When I said DA, what I mean is Dual Action. I see on the Meguiar's site they now have a "DA" system which means Drill Activated". I have an actual Dual Action polisher that I use with the Mequiar's DA microfiber correction system.